Flight controls incident involving a Eurocopter AS350 B3, 88 km south of Port Hedland, Western Australia

A newly-published ATSB occurrence brief details a flight controls incident involving a Eurocopter AS350 B3, 88 km south of Port Hedland, WA.

What happened

On 27 July 2024, the pilot of a Eurocopter AS350 departed a mining airport in Western Australia. The helicopter flew about 10 NM to the east and landed at a pre-determined location to collect a team of surveyors. On landing, the pilot of the helicopter received a message from the surveyors who advised they required another hour at the site, the pilot then shut the helicopter down. Noting the strong and gusting wind conditions, they tied the main rotor blades down to prevent blade sailing or bouncing, they also noticed the tail rotor was “see-sawing” aggressively. The pilot then installed the tail rotor gust lock pin, which dampens the movement of the tail rotor when the aircraft is stationary and prevents any damage, and conducted their usual turnaround inspection of the helicopter.

Once the survey team had returned to the helicopter, the pilot untied the main rotor tie?downs and stored them in the helicopter’s rear locker. From the rear locker the pilot conducted a pre-flight walk-around to the front of the aircraft, however did not inspect the tail rotor or remove the tail rotor gust lock pin. The pilot reported they had not previously installed the gust lock pin in the field and the deviation from their standard aircraft configuration contributed to the occurrence.

The pilot conducted normal pre-start and pre-departure checks, they noted an unusual, mild vibration from the main rotor and tail rotor which they presumed to be caused by the strong gusting wind from the 3 o’clock position. The pilot took off and immediately became aware that the pedals were jammed in a neutral position and determined the cause to be the tail rotor gust lock pin still being in place.

The pilot then briefed the passengers regarding the nature of the emergency and the plan to divert back to the original take-off airport. The pilot telephoned the airport reporting officer via the Bluetooth in their helmet to advise of the emergency.

They then conducted the emergency procedure for jammed pedals and landed on the runway without incident. The pilot reported the landing was a gentle zero speed, no hover landing.

The helicopter was positioned on the runway preventing any further arrivals or departures until it could be removed. There was no operational impact to the airport whilst the helicopter was positioned on the runway.

The pilot advised the ATSB that there was no visual damage to the structure of the aircraft or to the tail rotor assembly. An engineering inspection confirmed no damage to the aircraft; however the gust lock pin was deformed in the horizontal axis. Due to this deformation, the manufacturer requested that the following parts be replaced: tail rotor pitch change spider bearing; tail rotor control lever; and all tail rotor control attaching hardware aft of the tail rotor control rod (long shaft) for pitch links, lever etc.

Safety action

The pilot’s awareness in determining the cause of the jammed pedals and their following actions to conduct a safe emergency landing at the airport, prevented the loss of control of the aircraft and potential injuries or fatalities to the occupants.

Safety message

This incident highlights the importance of a thorough pre-flight inspection, ensuring pilots follow a systematic procedure as per the aircrafts flight manual. If interrupted, it is best practice to start again from the beginning of the inspection to ensure nothing is missed.

As per the flight manual pilots should always check flight controls for free movement prior to engine start.

Further, anytime a pilot detects an unusual control feedback prior to take-off, it is recommended that pilots shut down the aircraft, complete a thorough inspection and contact the operators engineering provider to discuss the issue.

The operator reported that they have sought a customisation of the “remove before flight” tapes used on the tail rotor gust lock pin to increase their length and therefore visibility.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.